Many thanks to everyone for your advice. Several posted charts and they have been quite helpful. I happened to be in the town where I purchased my fifth wheel today and stopped by the dealership to pick up some RV Wash & Wax and a new heavier duty city water connection for my camper, so I asked the service manager about the tires. He said he didn't know why they told me I needed to get a set of 10 ply tires because what I have on it now is what I need. Thanks again!

Im surprised you dont have E range tires on your F-250 already. That powerstroke weighs a ton and the added support the tires give you by increased PSI would help stiffen that truck up for sure.

Go check out the door jamb sticker for recommended inflation and let us know what it says, im curious now as to why you dont have the heavier tires on that heavy truck.

It does have Load Range E tires. I messed up earlier when I said it had Load Range C. I had read on the tire where it has 6 plies, but it is a load range E. At any rate, due to the age of the tires and the fact that they are down to the wear bars, I am going to go ahead and put a set of Michelin E-rated tires on it.

Got my new Michelin LTX A/T2 275/70-18LREs put on this afternoon. They look great and ride very smoothly. I'm well pleased. They weren't cheap, but you get what you pay for. Thanks again for your replies.

Can LT tires be used in place of ST tires. Everything is the same except the letters LT & ST

Many Forum posts you will see say they are interchangeable; but this is the result of confusion over the LT designation. It is further blurred by some OEMs shipping trailer tires with LT designations as original equipment.

There are actually LT truck tires and LT trailer tires as well as the more common ST trailer tire designations. As I understand it, LT TRUCK tires must never be used on a camper. ST trailer tires or LT Trailer tires should only be used on trailers and never on trucks.

Many Forum posts you will see say they are interchangeable; but this is the result of confusion over the LT designation. It is further blurred by some OEMs shipping trailer tires with LT designations as original equipment.

There are actually LT truck tires and LT trailer tires as well as the more common ST trailer tire designations. As I understand it, LT TRUCK tires must never be used on a camper. ST trailer tires or LT Trailer tires should only be used on trailers and never on trucks.